On the basis of having success , such a test for raising penetration rate and reducing comprehensive drilling cost was also carried out in two small diameter holes , and a good result was achieved 在成功试验的基础上,开展了2口提高钻井速度、降低钻井综合成本的小井眼天然气欠平衡钻井试验,取得了较好的应用效果。